in reply to 'perl -p' ne 'cat'

My remark is not specific to the problem that grinder runs into. Many commands default to read the standard output when given no file parameters. If this is not the desired beheavior, on systems that support it, just append /dev/null, so if your list of file parameters happens to be empty, the command will not defaults to STDIN because the /dev/null device acts like an empty file.

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